But 1D star Louis - who is also currently on a world tour - suggested that the press and public should cut him a bit more slack.
"Although I don't know him personally, I do wish the press would take it easy on @justinbieber," he tweeted.
"I really do empathise with him, I don't see anything out of character in comparison to any other teenagers I know."
And meanwhile Biebs was applauding his own fans on Twitter following another gig at the London arena.
He wrote: "Still a little short of breathe tonight but was an incredible show. London fans go hard! 4 SOLD OUT O2 shows in a row!! #BLESSED."
Watch MTV News on the hour every hour on MTV - Sky Channel 126 and Virgin Channel 134